1. Field of the Invention
The present invention relates to an image stabilizer capable of stabilizing blurry images produced from movement and vibration upon shooting by moving a correcting lens in the direction perpendicular to an optical axis of a lens system so that the optical axis of the correcting lens is matched with the optical axis of the lens system, a lens apparatus including such an image stabilizer and an imager apparatus including such a lens apparatus.
2. Description of the Related Art
In recent years, performance of an imager apparatus such as a digital still camera and a video camera has been improved remarkably, and it became possible for anyone to easily shoot still pictures and moving pictures with high image quality and with high efficiency. Improved efficiency of such an imager apparatus owes to high performance of a lens, a CCD (charge-coupled device), that is, a solid-state image pickup device and an image processing circuit.
However, even though the lens, the CCD and the like can be made higher in performance, if hand shake occurs in photographer's hands by which a camera (imager apparatus) is held, blurring occurs in images with high resolution and shot images are blurred unavoidably. To solve this problem, a part of relatively expensive cameras is equipped with an image stabilizer capable of correcting images blurred by camera shake and the like upon shooting. However, cameras that require such image stabilizer are not professional-level cameras, and it is to be understood that image stabilizers are indispensable to consumer cameras for a large number of amateur photographers with less shooting experience.
In general, a demand for smaller and lighter cameras (imager apparatus) is strong and most of photographers like cameras which are light in weight and easy to carry. However, since an image stabilizer according to the related art is comparatively large in size, when such large image stabilizer is mounted on a camera body, the whole of the camera becomes large in size unavoidably, which is against a demand for making cameras smaller in size and lighter in weight. In addition, the image stabilizer according to the related art requires a large number of parts and a problem arises, in which a cost of cameras is increased as the number of parts is increased.
Cited Patent Reference 1, for example, has described this kind of an image stabilizer according to the related art. The Cited Patent Reference 1 has described an image stabilizer for use with optical equipment such as a video movie and a lens-barrel of lens using the image stabilizer. The image stabilizer described in this Cited Patent Reference 1 (hereinafter referred to as a “first related-art example”) is characterized as follows. In an image stabilizer capable of correcting blurred images by moving a part of a shooting lens relative to the optical axis within the vertical plane, this image stabilizer includes a lens holding frame for holding a correcting lens, a first guiding mechanism for guiding movement of the lens holding frame to the first direction relative to the optical axis within the vertical plane and a second guiding mechanism for guiding movement of the lens holding frame to the second direction perpendicular to the first direction. This image stabilizer further includes a first driver for driving the lens holding frame to the first direction, a second driver for driving the lens holding frame to the second direction and a position detector for detecting the position of the correcting lens. The first guiding mechanism and a part of the second driver or the second guiding mechanism and a part of the first driver are located at the position in which they are overlapping with each other as seen from the optical axis direction.
According to the image stabilizer having the above arrangement described in the Cited Patent Reference 1, since the guide shaft for moving the correcting lens and the coil or the magnet for driving the guide shaft are located at the position in which they are overlapping with each other when a pitch shifter and a yaw driver or a yaw shifter and a pitch driver are seen from the optical axis direction, effects such as to reduce the width and height of the image stabilizer can be expected.
Cited Patent Reference 2, for example, has described a second example of the image stabilizer according to the related art. The Cited Patent Reference 2 has described an image stabilizer for use with optical equipment such as a video movie and a lens-barrel of lens using the image stabilizer. The image stabilizer described in this Cited Patent Reference 2 (hereinafter referred to as a “second related-art example”) is characterized as follows. In an image stabilizer capable of correcting blurred images by moving a part of a shooting lens relative to the optical axis within the vertical plane, this image stabilizer includes a lens holding frame for holding a correcting lens. The correcting lens includes a first restricting portion for restricting a movement range of the correcting lens, a first guiding mechanism for guiding a movement of the lens holding frame to the first direction relative to the optical axis within the vertical plane and a second guiding mechanism for guiding a movement of the lens holding frame to the second direction perpendicular to the first direction. The image stabilizer further includes a first driver for driving the lens holding frame to the first direction, a second driver for driving the lens holding frame to the second direction, a position detector for detecting the position of the correcting lens and a fixing mechanism having a second restricting portion engaged with the first restricting portion to restrict a moving range of the correcting lens. The first and second restricting portions are located on the inside of the first and second drivers as well as nearly concentrically.
According to the image stabilizer having the above arrangement described in the Cited Patent Reference 2, since the movable restricting members are located between the correcting lens and the drivers on nearly a concentric circle relative to the optical axis and non-engagement members to be engaged with the restricting members are provided on a fixed frame in order to restrict the movement range of the correcting lens, the movable range of the correcting lens can be restricted within the movable portion. Thus, effects such as to construct a small image stabilizer can be expected.
Also, Cited Patent Reference 3, for example, has described a third example of the related-art image stabilizer. The Cited Patent Reference 3 has described a vibration isolator mounted on a camera and the like, the vibration isolator for detecting vibration of comparatively low frequency and preventing blurry images by using the detected vibration as blurry image preventing information. A vibration isolator described in this Cited Patent Reference 3 (hereinafter referred to as a “third related-art example”) includes a correcting optical mechanism located within a lens-barrel for holding a lens group and which deviates the optical axis of the lens group, a vibration detector for detecting vibration applied to the lens-barrel and a vibration isolation controller for driving the correcting optical mechanism based on a signal from the vibration detector to isolate vibration. The correcting optical mechanism includes a correcting lens, a fixed frame for fixing the correcting lens, a first holding frame for holding the fixed frame in such a manner that the fixed frame can be moved in the first direction different from the optical axis direction of the lens group, a second holding frame for holding the first holding frame in such a manner that the first holding frame can be moved in the second direction different from the optical axis direction and the first direction and which is fixed to the lens-barrel of the lens. The correcting optical mechanism further includes first and second coils for moving the first and second holding frames in the first and second directions, first and second drivers formed of first and second magnetic field generating members opposed to the first and second coils and first and second position detectors for detecting amounts in which the fixed frame and the first holding frame are moved in the first and second directions. At least one of the first and second magnetic field generating members and the first and second position detectors are provided on a fixed member fixed to the lens-barrel of lens and which contains the second holding frame.
According to the vibration isolator having the above arrangement described in the Cited Patent Reference 3, there can be expected the effect in which the vibration isolator can respond to vibrations up to high-frequency vibrations without increasing the cost and the large space.
[Cited Patent Reference 1]: Japanese Published Patent Application No. 2000-258813
[Cited Patent Reference 2]: Japanese Published Patent Application No. 2003-270695
[Cited Patent Reference 3]: Japanese Published Patent Application No. 3-186823
However, while the first to third related-art examples include the position detector to detect the position of the correcting lens, the position detector in any of the above cases is composed of a light-emitting device formed of a light-emitting diode (LED) and a light-receiving device formed of a position sensitive diode (PSD). In the case of the third related-art example, the light-emitting device is attached to a stator and the light-receiving device is attached to the second holding frame, and the position of the fixed frame relative to the first holding frame in the pitch direction may be detected in relation to the light-emitting device and the light-receiving device.
In this case, the light-emitting device and the light-receiving device should be positioned properly after they were attached to the stator and the second holding frame. Since the central portions of the light-emitting device and the light-receiving device could not be visually confirmed, it was difficult to properly position the light-emitting device and the light-receiving device and a problem arises, in which work efficiency required upon manufacturing is not so high. Also, since the position detector needs two kinds of special electronic devices such as the LED and the PSD, the number of parts is increased, which is not economical. Further, a problem arises, in which control of the whole of the apparatus in addition to the position detection becomes complex.